[1] The parish seat and largest city is Alexandria, which developed along the Red River of the South.

The parish was created in 1807 after the United States acquired this territory in the Louisiana Purchase.

In 1763, the land that is now Rapides Parish became the new home of the Apalachee tribe, who were settled there with the permission of Governor Kerlerec.

Some Native Americans had come after fleeing the British and their Creek Indian allies from what is now Leon County, Florida.

The first French settler was Vincent Porei, who was granted a small tract of land in July 1764 by the Civil and Military Commander of Natchitoches.

Nicolas Etienne Marafret Layssard arrived in December 1766, with the permission of Aubrey and Foucault, to establish a "tar works" in the pineries of Rapides, for naval stores.

The population of Alexandria is heavily Democratic, but voters in the white-majority Rapides Parish frequently favor Republican candidates in competitive presidential elections.

As of the 2020 United States census, there were 130,023 people, 48,975 households, and 32,667 families residing in the parish.

In 2016, Hillary Clinton suffered the worst defeat for a Democratic candidate in the county since Walter Mondale in 1984, Although her husband, Bill, won the parish in 1996 during his reelection bid, this stands as the last time Rapides Parish voted for a Democratic candidate.

[21] By 1993 the district had established a secondary school for students with behavior issues, called Redirection Academy.

That year, the U.S. federal court system stopped the district from establishing a magnet school for academically advanced students.